In some examples, a first router establishes a fault detection session between the first router connected to a routing area and an outside router assigned a forwarding address, the outside router located outside the routing area, and the forwarding address used by a second router of the routing area to send a data packet to the outside router. The first router detects, in the fault detection session, a fault associated with the outside router, and in response to detecting the fault associated with the outside router in the fault detection session, provides an indication to the routing area that the forwarding address is no longer accessible.